1. Field of the Invention
The present invention pertains to the hazardous waste molding art, and more particularly, to a staged mold and method for molding a first material and then encapsulating the first material with a second material.
2. Background Art
A process is described in U.S. Pat. No. 4,234,632 for the stabilization of solid wastes by molding. The solid waste material is mixed with thermosetting resin and is charged into a first mold where the material is compressed and subjected to heat to form a rigid agglomerate. The agglomerate is covered by powdered thermoplastic resin in a second mold and the powder is therein consolidated by heating and solidified by cooling to jacket the agglomerate on the top and sides. The jacketed agglomerate is then inverted in the mold. The untreated bottom of the agglomerate is covered with additional powdered thermoplastic resin that is heated and solidified. During the heating and solidification of the resin on the bottom, the resin fuses with the sides to complete the encapsulation of the agglomerate. The purpose of the present invention is to provide a commercially viable full scale production apparatus and method for practicing the process of the above described patent for treating hazardous wastes for final disposal.
Other methods of stabilization of solid wastes by molding produce waste agglomerates and then cover them by surface treatment including the spraying or dipping of the agglomerates in a suitable coating material such as asphaltum or wrapping in a wire mesh as disclosed in U.S. Pat. No. 3,330,088. Alternatively, the agglomerated wastes may be wrapped in a vinyl sheet as disclosed in U.S. Pat. No. 3,451,185. The large scale processes described in these two patents are suitable for the management of general refuse but are unsuitable for achieving high performance management of low energy radioactive wastes and industrial hazardous wastes. The art described in U.S. Pat. No. 4,234,632, in contrast, yields stabilized hazardous wastes that resist harsh environmental stresses due to leaching, overburden, alternative wet and dry conditions, alternative freezing and thawing conditions, and mechanical impact.
Other methods of disposing of wastes include confining in plastic or metal containers, mixing wastes and binder materials such as cements and resins together, and solidifying mixtures of wastes and binders in containers. All of these methods have significant disadvantages. Both plastic and metal containers have a high relative initial cost. Containers are subject to such problems as ineffective sealing and corrosion which eventually allows leaching and seepage of the contents. Containment of wastes in cement or resin binders pose similar cost and leaching problems. Even the combination of confining waste and binder mixtures in containers does not assure effective waste stabilization due to the shortcomings of the containers.
Therefore, currently available large scale waste handling techniques are expensive and unsuitable for the management of hazardous wastes for final disposal because the potential exists for leaching and seepage of the wastes. Consequently, a need exists for improvements in the large scale management of hazardous wastes.